vMix Call has it's own mix minus so if the caller is hearing themself then that loop isn't happening inside vMix itself.

Your livewire mixer must be feeding the vMix audio back to the vMix machine.

So you have to configure your livewire mixer to send everything on your livewire network back to vMix EXCEPT for vMix itself.

So if you are using an Axia audio console there should be a dropdown box to automatically configure the vMix input as an automatic mix minus which is a feature of Axia, then you specify the return path of the mix-minused audio (could be a physical XLR output or a livewire output).

Every single fader on an Axia console has it's own independant mix Minus. I think you can select "Remote" or "Hybrid" or something similar from the dropdown.

Best way to check if there is a loop is to play a video on vMix and see if you can see the audio meters move on the input vMix takes from the livewire network.

The same principal works in the other direction. When sending audio from vMix to Livewire you must setup a mix minus. For example, the "Audio Outputs" in vMix settings you select the livewire network as "A" then select "A" on every single audio source except for livewire itself. Otherwise people with headphones on livewire might hear an echo due to the processing delay in vMix